kinda working

flake.nix

@@ -1,15 +1,50 @@
 {
   description = "cuda kernel compilation with nix";
 
+  nixConfig = {
+    extra-substituters = [
+      "https://nix-community.cachix.org"
+    ];
+    extra-trusted-public-keys = [
+      "nix-community.cachix.org-1:mB9FSh9qf2dCimDSUo8Zy7bkq5CX+/rkCWyvRCYg3Fs="
+    ];
+  };
+
   inputs = {
     nixpkgs.url = "github:nixos/nixpkgs/nixpkgs-unstable";
   };
-
-  outputs = { self, nixpkgs }: {
-
-    packages.x86_64-linux.hello = nixpkgs.legacyPackages.x86_64-linux.hello;
-
-    packages.x86_64-linux.default = self.packages.x86_64-linux.hello;
-
+  outputs = {
+    self,
+    nixpkgs,
+    ...
+  }: let
+    system = "x86_64-linux";
+    pkgs = import nixpkgs {
+      inherit system;
+      config.allowUnfree = true;
+      config.cudaSupport = true;
+      config.nvidia.acceptLicense = true;
+    };
+  in {
+    packages."${system}" = {
+      # just one main.cu file for now
+      # compile it and place it to $out/bin/cuda-kernel
+      cuda-kernel = pkgs.stdenv.mkDerivation {
+        name = "cuda-kernel";
+        src = ./.;
+        buildInputs = with pkgs; [
+          cudatoolkit
+          cudaPackages.cuda_cudart
+          linuxPackages.nvidia_x11
+        ];
+        LD_LIBRARY_PATH = "${pkgs.linuxPackages.nvidia_x11}/lib";
+        buildPhase = ''
+          nvcc -o main main.cu
+          mkdir -p $out/bin
+          mv main $out/bin/cuda-kernel
+        '';
+      };
+      default = self.packages."${system}".cuda-kernel;
+    };
   };
 }